%I #20 Aug 27 2023 19:28:00
%S 1,1,3,12,64,405,3312,44370,2209839,623492664
%N Number of self-converse semigroups of order n.
%H Andreas Distler, <a href="http://hdl.handle.net/10023/945">Classification and Enumeration of Finite Semigroups</a>, A Thesis Submitted for the Degree of PhD, University of St Andrews (2010).
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Semigroup.html">SemiGroup.</a>
%H <a href="/index/Se#semigroups">Index entries for sequences related to semigroups</a>
%F a(n) = A001423(n)*2 - A027851(n).
%Y Cf. A001426.
%K nonn,hard,more,nice
%O 0,3
%A _Christian G. Bower_, Jan 27 1998, updated Feb 19 2001
%E a(8) and a(9) from _Andreas Distler_, Jan 17 2011